Ensemble romantic comedy The Big Wedding tells the story of long divorced Don (Robert De Niro) and Ellie Griffin (Diane Keaton) who pretend they are still married at their adopted son's wedding in order to please the guest of honor, his ultra conservative birth mother. Katherine plays Lyla, Don and Ellie's daughter and sister to the groom.

The Griffin's soon learn acting the happily married couple is not so easy. The bride (Amanda Seyfried) and groom (Ben Barnes), and the whole family (Susan Sarandon, Katherine Heigl, Topher Grace) look on in amusement as their past, present and future unravel for all to see, trying not to kill each other in the process.

An official web site for the movie at thebigweddingmovie.com and a Facebook page have been launched for the Nu Image / Millennium Films production which is distributed by Lionsgate. The film was written and directed by Justin Zackham.